The present invention relates to heat transfer apparatuses with a zigzag passage and more particularly to a heat transfer apparatus with a zigzag passage which can be effectively used for plate-type heat exchangers or zigzag heat pipes.
Conventionally, to cool down electronic devices, an air cooling system has been frequently used with heat radiation members (heat sinks) such as fins that are in close contact with the heat generating portion of the devices. However, when heat cannot be dissipated desirably into the air and a high level of cooling is required, a forced cooling device that employs a liquid such as water having a high specific heat is used instead of or in conjunction with the air cooling system. In the latter case, frequently used is a plate-type heat exchanger which can be easily handled and readily brought into contact with a heat generating portion of the electronic device.
The plate-type heat exchanger of this type includes one with a zigzag pipe shown in FIG. 18 and another with plates affixed thereto shown in FIG. 19. First, the plate-type heat exchanger with a zigzag pipe shown in FIG. 18 has a metallic pipe with good heat conductivity, which has a predetermined diameter and is formed into a zigzag pipe in the same plane by folding the pipe in a U-shaped configuration at given lengths. A plate or plates with good heat conductivity are brazed to one or both sides of the zigzag pipe. On the other hand, the one shown in FIG. 19 has a zigzag groove which is folded at a given length of the groove in the general shape of the letter xe2x80x9cUxe2x80x9d or rectangle at least on one plane of the opposite surfaces of a pair of plates. The plates are affixed to each other to form a zigzag passage.
In addition, though not shown, such a heat exchanger is also known in which a raw metal sheet is pressed to form a plate with projections (ridges) for forming passages. A pair of the plates having a target shape is brazed to each other at the top end portion of the projections (ridges) to form the passages.
However, the aforementioned heat transfer apparatus with a zigzag passage could not allow a metal pipe to be bent in a zigzag manner with a small curvature at the U-turn portions. (For example, a pipe of pure copper cannot be provided with a minimum bending radius approximately 1.5 times the outer diameter of the pipe.) Accordingly, this allowed the pitch of adjacent passages to be narrowed within limitation.
In addition, to provide grooves requiring a depth for the plates, it was considerably difficult to make the wall between adjacent grooves thinner than approximately 0.5 mm in thickness, by general cutting methods from the viewpoint of cutting cost and durability.
Furthermore, taking pressed plates to be brazed to each other at the top end portion of the projections (ridges). In this case, a certain width is required of the abutting joint portion of the projections (ridges). This caused adjacent passages to be spaced apart by the amount of the joint width and therefore the pitch between adjacent passages could be narrowed within limitation.
As described above, it was difficult to narrow the pitch between adjacent fluid passages of the conventional plate-type heat transfer apparatus. Therefore, the cooling area (heat exchange area) per unit heat transfer area could be enlarged with limitation, thereby making it impossible to improve heat transfer efficiency and causing an increase in cost due to the difficulty of cutting.
In view of the aforementioned circumstances, the present invention is to realize a simple zigzag piping structure which allows the walls between adjacent passages to be made thinner and sturdy and thereby provide a low-cost heat transfer apparatus having a good heat efficiency.
To solve the aforementioned problems, a heat transfer apparatus with a zigzag passage according to a preferred embodiment of the present invention comprises a pair of opposed plates opposite to each other with at least one of the pair of the opposed plates forming a heat transfer surface; a bent plate, having a wavy cross-sectional shape, for forming rectangular grooves opposite to each other in a cross section of the passage so as to divide a space between said opposed plates into a plurality of side-by-side passages; and a pair of cover members bonded to said bent plate at both ends of the rectangular grooves of said bent plate and forming connecting portions between said side-by-side passages. The heat transfer apparatus with a zigzag passage is characterized in that one side wall portion of both side wall portions of the rectangular grooves of said bent plate is coupled to one end cover member of said rectangular grooves, the other side wall portion of both side wall portions of said rectangular grooves is coupled to the cover member on the other end of said rectangular grooves, and thus a zigzag passage is formed in which one side of the rectangular groove is folded to oppose the other side of the rectangular groove. In this configuration, the bent plate can be easily manufactured by pressing or the like. In addition, said side wall portion or a rib between adjacent passages is provided with a thickness of the plate-shaped material for forming the bent plate, thereby being made thin and sturdy. This allows the spacing between adjacent passages to be narrowed. Furthermore, the bent plate can be bonded to the opposed plates at a wide area using the bottom wall portion of said rectangular grooves, thereby making it possible to provide a sufficient bonding strength.
In the aforementioned heat transfer apparatus with a zigzag passage, it is preferable that on any one of a crest or trough of a waveform of said bent plate, provided are one bottom wall extended portion formed by extending the bottom wall portion of said rectangular grooves toward both ends and another bottom wall extended portion; said one side wall portion is extended to one side of said rectangular grooves and said other side wall portion is extended to the other end of said rectangular grooves to provide one side wall extended portion and another bottom wall extended portion; and said one bottom wall extended portion and said one side wall extended portion are coupled to the cover members on one end of said rectangular grooves and said other bottom wall extended portion and said other side wall extended portion are coupled to a cover member on the other side of said rectangular grooves. In this configuration, the bent plate is provided with the side wall extended portion and the bottom wall extended portion, thereby making it possible to facilitate the attachment of the cover members.
In this case, it is more preferable that said bottom wall extended portion is extended sideward of the side wall extended portion of adjacent rectangular grooves, a portion extended sideward of said bottom wall extended portion and said side wall extended portion of the adjacent rectangular grooves are integrally coupled to each other by a plate-shaped coupling portion opposite to the side wall extended portion of the adjacent rectangular grooves; and said one side wall extended portion is integrally formed via said one bottom wall extended portion as well as said other side wall extended portion is integrally formed via said other bottom wall extended portion. In this configuration, the bent plate is provided with no projections, and allows the opposed plates and the cover members to be readily bonded thereto and easily handled. Moreover, it is made possible to shear and bend the bent plate by pressing or the like.
The present disclosure relates to the subject matter contained in Japanese patent application No. 2000-47961 (filed on Feb. 24, 2000), which is expressly incorporated herein by reference in its entirety.